The present invention relates to a multilayer ceramic capacitor; and, more particularly, to a novel structure of conductive layers therein.
Referring to FIG. 1, there is illustrated a partial cutaway perspective view of a conventional multilayer ceramic capacitor. The multilayer ceramic capacitor 100, as shown in FIG. 1, includes a laminated body 103 having alternately stacked ceramic dielectric layers 101 and conductive layers 102 and a pair of external electrodes 104-1, 104-2 respectively disposed at two opposite end portions of the laminated body 103. The conductive layers 102 are alternately connected to the external electrodes 104-1, 104-2: that is, the external electrode 104-1 is connected to every second conductive layer and the external electrode 104-2 is coupled with the remaining conductive layers not connected to the external electrode 104-1. The ceramic dielectric layers 101 and the conductive layers 102 have flat surfaces. Further, the thickness of the conductive layers 102 is spatially uniform without local variation. When a voltage is applied between the external electrodes 104-1, 104-2, the multilayer ceramic capacitor 100 stores electric charges in the conductive layers 102, thereby producing electric fields between every two neighboring conductive layers.
Nowadays, multilayer ceramic capacitors are required to be further scaled down but with higher capacitance. Such tasks, however, may not be successfully achieved with the capacitor 100. Accordingly, different types of multilayer ceramic capacitors have been proposed for that purpose. In FIG. 2, there is illustrated a cutaway perspective view of one of such improved prior art multilayer ceramic capacitors. A multilayer ceramic capacitor 100a shown in FIG. 2 differs from the conventional multilayer ceramic capacitor 100, in that the conductive layers 102a of the capacitor 100a are corrugated. As a result, the contact area between the conductive layers 102a and the ceramic dielectric layers 101a in capacitor 10a becomes larger than that in the capacitor 100 and, therefore the capacitance of the capacitor 100a increases.
Since, however, it is relatively difficult to make the corrugated conductive layers very thin, the ability to realize the miniaturization of multilayer ceramic capacitors with large capacitance by employing an increased number of such corrugated layers is inherently limited. Further, the corrugated conductive layers 102a require the use of a greater amount of conductive paste than the flat conductive layers 102. Generally, the conductive paste used in forming the conductive layers contributes to a large portion of the manufacturing cost of a multilayer ceramic. Therefore, the use of corrugated conductive layers would lead to an increased manufacturing cost.
It is, therefore, an object of the present invention to provide a miniaturized large capacitance multilayer ceramic capacitor with a low manufacturing cost.
In accordance with one aspect of the present invention, there is provided a multilayer ceramic capacitor, comprising:
a laminated body formed by alternately stacked ceramic dielectric layers and conductive layers,
wherein the interfaces between the ceramic dielectric layers and the conductive layers are corrugated and the conductive layers have a nonuniform thickness.
The conductive layers are provided with interrupted regions devoid of a conductive material and the boundary portions of the conductive layers close to the interrupted regions are curved upward or downward along the stacking direction of the ceramic dielectric layers and the conductive layers.
In accordance with another aspect of the present invention, there is provided a method for forming a multilayer ceramic capacitor, comprising the steps of:
stacking ceramic green sheets having a conductive paste coated thereon; and
pressing the stacked ceramic green sheets with a die having grooves on a pressing surface thereof, wherein an average depth of the grooves is between about 10 and 30% of an average thickness of a ceramic green sheet.